Citroen C5 X7 rear brakes sticking

[yoseff]

Happy new year!

After changing front pads and rotors with success,

i decided to do the same in the rear. Seemed not too hard , and i own a Lexia , so what could go wrong?

Did all the procedures , but after a few days i realized had a stuck rear caliper. It overheated to the point of seeing some decoloration on disc painted parts.

Disassemble it, cleaned it and used a repair kit (minus the piston and the hand brake side)
Everything was looking good, but after reassembly and bleed, still seized...

Decided to get a new caliper (Got one from Comline - seems to have good quality at a good price,besides being available in the next morning to fit) and after assembly, bleed it and wheel still not free to spin!

I was obviously in disbelief. What could be?
On more detailed inspection i realized that without this wire , wheel was spinning , but as soon as i put the wire , caliper would turn a bit , braking the wheel with the corners of the brake pads.

Could it be that the support or the sliding pins are bent? Could it be that the sliding pins are worn allowing too much wobbling to the sides , provoking that?
Would like to get some shared experiences from you regarding to that.
For now i modified the wire for it not to force caliper to the front. Wanna get a new set of wires to try.
Rear rotors are around 50º Celsius without much speed or braking , just normal ride on national road, sometimes going a bit above 60º. Front ones are almost completely cold

As i changed brake fluid recently for ATE TYP 200 , im waiting to get a bit more of it to give a good bleed on all 4 wheels again. Wanna also to bleed with Lexia. Can that help with a better return of the rear pistons on the rear calipers?

Thanks in advance for your help on this matter.

[MattBLancs]

Just a thought, not C5 specific, but I've read of brake flexi hoses partially collapsible internally and acting like a one-way valve: brakes not released by this "effect".

How does the Flexi hoses look?

[bobins]

The workshop manual makes reference to calibrating the handbrake after fitting rear brake pads - I presume you've done this ?

C5 brake calibration

Also - if your pads look like this then the pads with the spring on them go on the inboard side

C5 rear pads

Sprung pad on inside

[yoseff]

Just a thought, not C5 specific, but I've read of brake flexi hoses partially collapsible internally and acting like a one-way valve: brakes not released by this "effect".

How does the Flexi hoses look?

That's surely a possibility, specially because it still the original flexi hoses (car is from 2011 with 511000km)

I suspect that in any eventuality (even if support was a bit bent and caliper worked a bit more sideways) the piston should return.

[yoseff]

The workshop manual makes reference to calibrating the handbrake after fitting rear brake pads - I presume you've done this ?



Also - if your pads look like this then the pads with the spring on them go on the inboard side

Yes, i performed calibration and that pad with spring is in the inside.
These are the pads i fitted

Basically i followed the procedure in this video for the rear ones:

[PaulC5]

If the hoses are stopping brake fluid returning then with the wheel off the ground if it is still binding then slacken the bleed screw and if the hose or something else is preventing fluid going back then the brake should release.

Other things to consider include there may be too much paint on the pads ends so they are not a loose fit in the carrier, the pads ends might not be smooth or the carrier might need a bit more cleaning up so the pads can slide easily. I always put a bit of copper grease on the pad ends and carrier where they slide. The caliper should be able to slide on its bolts so these should be clean and a bit of copper grease helps.

[yoseff]

If the hoses are stopping brake fluid returning then with the wheel off the ground if it is still binding then slacken the bleed screw and if the hose or something else is preventing fluid going back then the brake should release.

Other things to consider include there may be too much paint on the pads ends so they are not a loose fit in the carrier, the pads ends might not be smooth or the carrier might need a bit more cleaning up so the pads can slide easily. I always put a bit of copper grease on the pad ends and carrier where they slide. The caliper should be able to slide on its bolts so these should be clean and a bit of copper grease helps.

Today has been raining quite a bit, so only tomorrow or Sunday will go back to it and double check it.
I actually checked before and they are actually quite free to travel. I also used ceramic grease from liqui moly.

I was also told that the guide pins are often bent when disassembly / assembly is not done in a careful way , so i'll be changing those guide pins too.

At the moment is not sticking too much, but still have a bit more friction than id want

[yoseff]

Quick update:
New flexible hose - fitted
New guide pins - fitted
Bleed (in that wheel) - done
New steel wire in caliper - as soon as is put, caliper twists a bit and small portions of brake pads continue to brake the wheel.

What am i missing here?
Waiting to get more Dot4 (Ate TYP 200, the one i have there) in order to do an exhaustive bleed, including the one with Diagbox, that had not done yet. Can that play a role?

At this point all is new in that brake side, but the caliper support. Can it be that it is slightly bent?

This has been a tough one to solve, and while i do it, i'm ruining new disc and pads... Dammn.

The solution for use the car in the meanwhile has been a modified wire that doesn't push the caliper... Temperatures of the disc on normal use at average speeds (national road and city) are around 60º Celsius.

More ideas, please?

[PaulC5]

On that type of caliper I think have also put copper grease in the wire/caliper holes so it does not rust up and where the wire slides on the carrier.

[Stickyfinger]

A Caliper should NEVER "move" or twist....all it should do is slide on its pins in one axis only (I know it is called a "floating Caliper" ) I would check for a problem in the slide surface/bearing with the caliper/guide pins......."slop" should be minimal, almost undetectable to finger pressure/wiggle when dry and nothing when lubricated.

[Kees]

Maybe you should look at the electric handbrake system, it's possible, that the caliper sits not right at the pin inside.

[yoseff]

On that type of caliper I think have also put copper grease in the wire/caliper holes so it does not rust up and where the wire slides on the carrier.

It's a good idea, but i change anything where copper paste would be used with ceramic paste, to avoid the possibility of galvanic corrosion

[yoseff]

A Caliper should NEVER "move" or twist....all it should do is slide on its pins in one axis only (I know it is called a "floating Caliper" ) I would check for a problem in the slide surface/bearing with the caliper/guide pins......."slop" should be minimal, almost undetectable to finger pressure/wiggle when dry and nothing when lubricated.

Totally agree. Maybe the new caliper brings defective rubber parts? (where the pin moves)
Since the pins are new, it's another part i can try to change and i have 2 new sets here to try

[yoseff]

Maybe you should look at the electric handbrake system, it's possible, that the caliper sits not right at the pin inside.

I have a tendency to keep the handbrake aside of this issue as the cables are loose when park brake is not applied. Or is there another issue that i misunderstood?

[yoseff]

Could the "secondary brake system" not being bleed yet, play any role on a sticking brake ? I changed the fluid but didnt do the secondary bleed, just the main one.